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Federal Register / Vol. 86, No. 185 / Tuesday, September 28, 2021 / Proposed Rules
53589

TABLE 2CURRENT RESILIENCY OF THE PEN ASCO LEAST CHIPMUNK POPULATIONS
Demographic factors
Population
White Mountains
Sacramento Mountains

Trap rate number individuals/
trap hour surrogate for density
Population trends
Population connectivity
Low
1.5
Very Low
2

Low
1
Very Low
2

Very Low
2
Very Low
2

See the SSA report for the complete current condition analysis for the Penasco least chipmunk Service 2018, pp. 5465.
Risk Factors for Penasco Least Chipmunk We evaluated the past, current, and future stressors that affect the Penasco least chipmunks needs for long-term viability. Additionally, we evaluated several potential stressor sources that are not described here because the stressor source is predicted to have low impact on Penasco least chipmunk viability. More information on these stressors, including interspecific competition, scientific collection, and climate change can be found in the SSA
Service 2018, pp. 5052.
Stressors affecting the viability of the Penasco least chipmunk include vegetation shifts, wildfire, forest encroachment, recreation, development, and land use Factor A, disease Factor C, nonnative species Factors A and C, and small population size and lack of connectivity Factor E. Considerations under Factor D are described below.
Penasco least chipmunk habitat is afforded some protection under the Wilderness Act of 1964 16 U.S.C. 1131
1136. Within the White Mountains, approximately 54 percent of the current range of the Penasco least chipmunk is within the Lincoln National Forest White Mountain Wilderness Area. This designation limits management options and conservation efforts in designated wilderness areas to some degree. The Wilderness Act states that wilderness should be managed to preserve its natural conditions and yet remain untrammeled by man, and defines wilderness . . . as an area of undeveloped Federal land retaining its primeval character and influence, without permanent improvements or human habituation . . . 16 U.S.C.
11311136. Within designated wilderness areas, no commercial activities are permitted, no permanent or temporary roads, no motorized equipment or any form of mechanical transport, and no structures are
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Habitat factors
Subpopulations within populations
Available suitable habitat to support population persistence
Habitat availability trends
Habitat condition with land use or management
Very Low
2
Very Low
2

Moderate
0
Very Low
2

Moderate
0
Very Low
2

Moderate
0
Very Low
2

Condition category
Low.
1.
Very Low.
2.

Vegetation Shifts, Wildfire, and Forest Encroachment
have resulted in the additional stressor source of altered fire regimes.
Forest encroachment into grasslands is occurring in both the Sacramento Mountains and in the White Mountains, although the causes for each are likely different. The causes for tree encroachment into meadows in the Sacramento Mountains is likely related to land use and land management practices, while the White Mountains are influenced by climatic events and successional encroachment processes.
While some landscape restoration projects are planned i.e., the South Sacramento Forest Restoration Project that may address some areas of meadow encroachment, no additional projects are planned within the historical range of the Penasco least chipmunk either in the Sacramento Mountains or the White Mountains to control or limit tree encroachment into meadow habitat.

Over the last 150 years, land management practices have shifted the vegetative components of Penasco least chipmunk habitat in the Sacramento Mountains, resulting in an overall lack of suitable habitat for the subspecies.
The historically open, park-like stands of ponderosa pine forest that comprised Penasco least chipmunk habitat have been replaced with high-density, smalldiameter ponderosa pine, with encroaching Douglas fir Pseudotsuga menziesii and white fir Abies concolor, and a lack of native grass meadow habitat Service 2018, pp. 39
41.
These changes in vegetation composition inclusion of less firetolerant species of trees such as Douglas fir and white fir and structure from low-density, large-diameter trees with few low branches to high-density, smalldiameter trees with many low branches, coupled with the loss and conversion of native to nonnative grass meadows, alter the suitability of the habitat for the Penasco least chipmunk in the Sacramento Mountains. Effective fire exclusion and suppression actions have also contributed to the changes in forest composition and structure and
Recreation, Development, Land Use, and Land Management Agricultural land use in the Sacramento Mountains appears to have shifted from cultivation in the early part of the 20th century to pasture use. This conversion likely affected a potentially significant food resource i.e., crops for Penasco least chipmunks in the Sacramento Mountains, specifically James Canyon Service 2018, p. 42. It is likely that the high-quality, abundant food resource of wheat and oat fields drew Penasco least chipmunks to the fields and roads where the animals were easily observable, as early records noted that Penasco least chipmunks were especially abundant along rail fences, eating oats and wheat at field edges Bailey 1931, p. 91. However, Penasco least chipmunks were also abundant in the open, mature ponderosa pine forests Bailey 1931, p. 91. Penasco least chipmunks were noted as abundant throughout the Sacramento Mountains during the early 1900s, in both natural open habitat and near agricultural fields Service 2018, p. 43. The change in land use from crop fields to pasture for livestock likely impacted Penasco least chipmunks by decreasing the
permitted within the area 16 U.S.C.
11311136. Habitat for the Penasco least chipmunk appears to be relatively unaltered in the White Mountains Wilderness Area, except for the encroachment of trees into meadows Service 2018, p. 35.
Additionally, the range of the Penasco least chipmunk overlaps with designated Mexican spotted owl critical habitat; the management of that habitat for the Mexican spotted owl does allow for some level of grazing. This may result in changes to the plant community that do not adversely affect the prey base of the Mexican spotted owl but is detrimental to the specific plant community needs of the Penasco least chipmunk Service 2018, pp. 38
40.

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